1. Field of the Invention
This invention relates to the launching of light into optical fibre-bundles and particularly to a novel coupling arrangement between the fibre ends.
2. Description of the Prior Art
Optical coupling between one fibre-bundle and another may be achieved by polishing the ends of the bundles and placing a polished end of one bundle in close proximity with one of the polished ends of the other bundle. Unless special measures are taken to ensure that the ends of individual fibres of the first bundle all register exactly with the ends of fibres of the second bundle the randomness of registration will contribute to optical loss in the coupling. Some of the light will not be launched into the cores of the fibres of the second bundle but will be lost through being launched either into the cladding or into the interstices between fibres. In a typical close packed multi-mode optical fibre-bundle only about 60% of the total cross section of the bundle is provided by the fibre cores, and hence the loss arising from lack of registration will be a significant proportion of the total loss of such a coupling. This problem of launching efficiency is not confined to the launching of light from one fibre-bundle into another, but is a general problem affecting the launching of light into a fibre-bundle from any light source.